its basic breeding knowledge. the species of the pokemon in the egg is determine by the mother, the father pass on moves. So if you have a male pokemon and you want the baby evolution of that pokemon you have to get a female version of that pokemon or a ditto.

Breeding a Pokemon always result in the lowest evolution and it will always be at lv 1. The only exception is baby Pokemon, since they require the parents to hold a special item. Sadly, Ghastly is a normal Pokemon, so you have to train it.
Source: http://pokemondb.net/mechanics/breeding